Sancho II of Castile

Sancho II of Castile (1035-7 October 1072) was the King of Castile from 1065 to 1072, succeeding Fernando I of Castile and preceding Alfonso VI of Leon, and King of Galicia from 1071 to 1072, succeeding Garcia II of Galicia and preceding Alfonso VI. Sancho defeated Navarre and Aragon in the War of the Three Sanchos with help from his brother Alfonso, but when he turned on Alfonso and besieged Zamora, he was assassinated by a Leonese noble.

Biography
Sancho Jimena was a Catholic of the House of Jimena, and was the son of Fernando I of Castile and Sancha of Leon. Sancho was their oldest child, and when his father died in 1065, Sancho was given the Kingdom of Castile. Sancho was also blessed with the talents of El Cid, a Spanish nobleman who became a symbol of the Reconquista. El Cid defeated Aragon at the Battle of Graus in 1063, killing Ramiro I of Aragon. Sancho also feuded with his cousins Sancho IV of Navarre and Sancho of Aragon in 1068, and he reconquered Bureba, Alta Rioja, and Alava from Navarre; Fernando gave these lands to Garcia III of Navarre in return for aid against Bermudo III of Leon. He allied with his brother Alfonso VI of Leon against the two other Sanchos despite defeating him at Llantada in a recent feud, and they conquered Galicia. Despite agreeing to partition Galicia, Sancho turned on Alfonso and invaded Leon, forcing him out of Toledo. On 12 January 1072, Sancho was crowned King of Leon.

However, Sancho was assassinated on 7 October 1072 while besieging the Leonese stronghold of Zamora, held by his sister Countess Urraca of Zamora and Leonese defenders. The Leonese noble Vellido Dolfos pretended to be a deserter and entered Sancho's camp, and he headed to tell Sancho of a weakness in the city's defense. However, Dolfos used Sancho's own sword to impale him in the back. The Castilians were defeated, and Alfonso VI of Leon also became King of Leon, uniting Castile and Leon under one man.